Better error for Java annotation nested in a Scala ConstantAnnotation

Java supports nested annotations as constant annotation arguments, but
Scala's ConstantAnnotation doesn't. Better error message for this case.

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -3858,7 +3858,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
      * Convert an annotation constructor call into an AnnotationInfo.
      */
     @nowarn("cat=lint-nonlocal-return")
-    def typedAnnotation(ann: Tree, annotee: Option[Tree], mode: Mode = EXPRmode): AnnotationInfo = context.withinAnnotation {
+    def typedAnnotation(ann: Tree, annotee: Option[Tree], mode: Mode = EXPRmode): AnnotationInfo = {
       var hasError: Boolean = false
       var unmappable: Boolean = false
       val pending = ListBuffer[AbsTypeError]()
@@ -3921,7 +3921,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
       // begin typedAnnotation
       val treeInfo.Applied(fun0, _, argss) = ann
       if (fun0.isErroneous) return finish(ErroneousAnnotation)
-      val typedFun = typed(fun0, mode.forFunMode)
+      val typedFun = context.withinAnnotation(typed(fun0, mode.forFunMode))
       if (typedFun.isErroneous) return finish(ErroneousAnnotation)
 
       val Select(New(annTpt), _) = typedFun: @unchecked

test/files/neg/annots-constant-neg.check

@@ -43,54 +43,68 @@ Test.scala:40: error: annotation argument cannot be null
 Test.scala:43: error: annotation argument needs to be a constant; found: java.lang.Integer.TYPE
   @JAnn(value = 0, b = java.lang.Integer.TYPE) def t16 = 0 // err
                                          ^
-Test.scala:47: error: annotation argument needs to be a constant; found: Test.this.nonConst
+Test.scala:48: error: nested classfile annotations must be defined in java; found: inline
+  @JAnn(value = 0, c = Array(new inline)) def t18 = 0 // err
+                             ^
+Test.scala:52: error: annotation argument needs to be a constant; found: Test.this.nonConst
   @Ann(nonConst) def u3 = 0 // err
        ^
-Test.scala:49: error: not enough arguments for constructor Ann: (value: Int, a: String, b: Class[_], c: Array[Object]): Ann.
+Test.scala:54: error: not enough arguments for constructor Ann: (value: Int, a: String, b: Class[_], c: Array[Object]): Ann.
 Unspecified value parameter value.
   @Ann() def u4 = 0 // err
    ^
-Test.scala:56: error: annotation argument cannot be null
+Test.scala:61: error: annotation argument cannot be null
   @Ann(value = 0, a = null) def u10 = 0 // err
                       ^
-Test.scala:57: error: annotation argument needs to be a constant; found: Test.this.getClass()
+Test.scala:62: error: annotation argument needs to be a constant; found: Test.this.getClass()
   @Ann(value = 0, b = getClass) def u11 = 0 // err
                       ^
-Test.scala:58: error: Array constants have to be specified using the `Array(...)` factory method
+Test.scala:63: error: Array constants have to be specified using the `Array(...)` factory method
   @Ann(value = 0, c = new Array(1)) def u12 = 0 // err
                       ^
-Test.scala:61: error: annotation argument needs to be a constant; found: java.lang.Integer.TYPE
+Test.scala:66: error: annotation argument needs to be a constant; found: java.lang.Integer.TYPE
   @Ann(value = 0, b = java.lang.Integer.TYPE) def u16 = 0 // err
                                         ^
-Test.scala:66: error: multiple constructors for Ann1 with alternatives:
+Test.scala:69: error: Java annotation SuppressWarnings is abstract; cannot be instantiated
+Error occurred in an application involving default arguments.
+  @Ann(value = 0, c = Array(new SuppressWarnings(value = Array("")))) def u17 = 0 // err
+                            ^
+Test.scala:69: error: not found: value value
+Error occurred in an application involving default arguments.
+  @Ann(value = 0, c = Array(new SuppressWarnings(value = Array("")))) def u17 = 0 // err
+                                                 ^
+Test.scala:71: error: annotation argument needs to be a constant; found: new scala.inline()
+  @Ann(value = 0, c = Array(new inline)) def u18 = 0 // err
+                            ^
+Test.scala:76: error: multiple constructors for Ann1 with alternatives:
   (s: String)Ann1 <and>
   (value: Int)Ann1
  cannot be invoked with (x: String)
   @Ann1(x = "") def v4 = 0 // err
    ^
-Test.scala:68: error: Ann1 does not take parameters
+Test.scala:78: error: Ann1 does not take parameters
   @Ann1(0)(0) def v6 = 0 // err
    ^
-Test.scala:69: error: not enough arguments for constructor Ann2: (x: Int)(y: Int): Ann2.
+Test.scala:79: error: not enough arguments for constructor Ann2: (x: Int)(y: Int): Ann2.
 Unspecified value parameter x.
   @Ann2 def v7 = 0 // err
    ^
-Test.scala:70: error: missing argument list for constructor Ann2 in class Ann2
+Test.scala:80: error: missing argument list for constructor Ann2 in class Ann2
   @Ann2(x = 0) def v8 = 0 // err
    ^
-Test.scala:73: error: no arguments allowed for nullary constructor Ann3: (): Ann3
+Test.scala:83: error: no arguments allowed for nullary constructor Ann3: (): Ann3
   @Ann3(0) def v11 = 0 // err
         ^
-Test.scala:74: error: not enough arguments for constructor Ann4: (x: Int, value: Int): Ann4.
+Test.scala:84: error: not enough arguments for constructor Ann4: (x: Int, value: Int): Ann4.
 Unspecified value parameter value.
   @Ann4(0) def v12 = 0
    ^
-Test.scala:80: error: no arguments allowed for nullary constructor Ann5: (): Ann5
+Test.scala:90: error: no arguments allowed for nullary constructor Ann5: (): Ann5
   @Ann5(0) def v18 = 0 // err
         ^
-Test.scala:71: warning: Implementation limitation: multiple argument lists on annotations are
+Test.scala:81: warning: Implementation limitation: multiple argument lists on annotations are
 currently not supported; ignoring arguments List(0)
   @Ann2(x = 0)(y = 0) def v9 = 0 // warn
    ^
 1 warning
-28 errors
+32 errors

test/files/neg/annots-constant-neg/Test.scala

@@ -42,6 +42,11 @@ object Test {
   @JAnn(value = 0, b = classOf[Int]) def t15 = 0
   @JAnn(value = 0, b = java.lang.Integer.TYPE) def t16 = 0 // err
 
+  // nested annotation is ok
+  @JAnn(value = 0, c = Array(new SuppressWarnings(value = Array("")))) def t17 = 0
+  // but the nested annotation needs to be itself a Java annotation
+  @JAnn(value = 0, c = Array(new inline)) def t18 = 0 // err
+
   @Ann(1) def u1 = 0
   @Ann(const) def u2 = 0
   @Ann(nonConst) def u3 = 0 // err
@@ -60,6 +65,11 @@ object Test {
   @Ann(value = 0, b = classOf[Int]) def u15 = 0
   @Ann(value = 0, b = java.lang.Integer.TYPE) def u16 = 0 // err
 
+  // nested annotations are only allowed for Java annotations, not for Scala ConstantAnnotations
+  @Ann(value = 0, c = Array(new SuppressWarnings(value = Array("")))) def u17 = 0 // err
+  // the outer and the nested annotation need to be Java annotations
+  @Ann(value = 0, c = Array(new inline)) def u18 = 0 // err
+
   @Ann1() def v1 = 0
   @Ann1(0) def v2 = 0
   @Ann1(value = 0) def v3 = 0